Owing to the fact that light emitting diodes (LEDs) save more electricity than conventional light bulbs and also generate less heat, LEDs have been widely used in Christmas decoration lamp strings. Most LED lamp string structures generally use a single LED to replace the conventional tungsten filament lamp and assemble the LED with attached lamp filaments in advance. The tails of the lamp filaments are then bent to make electrical contact with the lamp terminals and assembled in the interior of the lamp socket. Assembly of the conventional LED structure with the attached lamp filaments causes difficulty in the manufacturing process. The conducting filaments of LEDs have greater tensile strength than the conventional lamp filaments, therefore it is not beneficial to replace the original LED filaments in order to form the lamp string.